Pitcher plant description

This impressive carnivorous plant belongs to a spectacular family of tropical Asian pitcher plants (Nepenthes species). Nepenthes lavicola is a climbing vine, capable of reaching a height of about three metres, and has modified pitcher-shaped leaves that hang from coiled tendrils (2). Nepenthes species usually have two or three different types of pitcher, generally known as upper and lower pitchers (4). The pitchers in Nepenthes lavicola are trumpet-shaped and are dark brown to purple in colour. The inside of the lower pitchers are pale green with red spots (2)(5). The pitchers contain an acidic fluid, secreted by the many glands which cover the inside surface of the lower half of the pitcher (4). The smooth and waxy upper inner surface of the pitcher makes it impossible for invertebrates that have fallen into the pitchers to gain a foothold (4), and a ridge of hardened tissue lining the mouth of the pitcher, the peristome, bears downward pointing teeth, also preventing insects from escaping (6). The peristome of Nepenthes lavicola is yellow-green, broad and flared (5), and a lid overhangs the mouth of the pitcher preventing rain water from diluting the pitcher fluid (6). The tendrils, pitchers and inflorescences of Nepenthes lavicola are all covered in short hairs (2)(6).

Related species

Pitcher plant biology

Pitcher plants are dioecious meaning that male and female flowers grow on separate plants (4), and only begin to flower once the upper pitchers are produced (6). During the early evening and night, the flowers produce large amounts of nectar which evaporates by morning. This nectar attracts flies during the early evening and moths at night to aid pollination. Once fertilised, the fruit of Nepenthes species usually takes about three months to develop and ripen. These fruits usually contain between 100 and 500 very light, winged, seeds, which can measure up to 30 millimetres long and are thought to be dispersed by the wind (4)(6). Despite enormous numbers of seeds being produced, only a few manage to germinate and only a fraction of those survive to maturity (6).

Carnivorous pitcher plants are adapted to grow in soils low in nutrients. Although the plants do gain some nutrition through the soil, and energy through photosynthesis, they supplement this with a diet of invertebrates, usually consisting of ants, cockroaches, centipedes, flies and beetles (4). Insects are attracted to the pitchers by their bright colours and nectar, which is secreted by glands situated on the lid and the peristome of the pitcher. The insects fall into the acidic fluid at the base of the pitcher and, unable to escape, they drown. Digestive enzymes are then released to break down the captured prey (4).

Despite the hostile environment of the pitchers, they can be home to number of animals, such as the red crab spider (Misumenops nepenthicola). The red crab spider inhabits pitcher plants in Indonesia, Malaysia and Singapore, ambushing insects that crawl into the pitcher and preying upon other insects, such as mosquitoes, as they emerge from larvae that live in the pitcher fluid (6).

Pitcher plant status

Pitcher plant threats

Nepenthes species are threatened by a combination of over-collection and habitat loss (6). In Indonesia, habitat destruction is a major problem, as a result of illegal and commercial logging and large agricultural projects such as rubber and oil palm plantations (7). Sumatra has a very high rate of habitat loss with some areas losing up to 65 percent of their forest cover in the last 25 years (8). Only 33.8 percent of Sumatra remains covered by primary forest, and only 1.3 percent of this is upper montane vegetation, in which Nepenthes lavicola is found. The highly localised distribution of Nepenthes lavicola makes it particularly susceptible to the impacts of habitat disturbance or catastrophic environmental events, such as drought or fire. In addition, highland plants, such as Nepenthes lavicola, take longer than lowland plants to recover from any disturbance as growth is slower (2).

Pitcher plant conservation

Nepenthes lavicola is listed on Appendix II of the Convention of International Trade in Endangered Species (CITES) which limits international trade in this species. However, this is very difficult to regulate. Trade in Nepenthes species does not need to be identified down to species level and plants simply labelled as Nepenthes accounted for 94 percent of exported plants between 1988 and 1993. This needs to be remedied and urgent attention is required to close other trade loopholes. Presently, over-collection does not seem to pose an extensive threat for Nepenthes lavicola and artificial cultivation reduces this threat further (2). Conservation efforts can be made more effective, not only by the implementation and enforcement of protective laws, but also by the encouragement of artificial propagation and establishment of habitat reserves (9).

Glossary

Proteins that trigger, or accelerate, activity in the cells of the body, for example, breaking down foods during digestion, and building new proteins..

Fertilisation

In a flowering plant, fertilisation is the process of a pollen grain joining with the ovule (female egg cell). After fertilisation, the female parts of the flower develop into a fruit.

Genus

A category used in taxonomy, which is below ‘family’ and above ‘species’. A genus tends to contain species that have characteristics in common. The genus forms the first part of a ‘binomial’ Latin species name; the second part is the specific name.

Inflorescences

The shoots of a plant which bears a group or cluster of flowers.

Invertebrates

Animals with no backbone.

Larvae

Stage in an animal’s lifecycle after it hatches from the egg. Larvae are typically very different in appearance to adults; they are able to feed and move around but usually are unable to reproduce.

Photosynthesis

Metabolic process characteristic of plants in which carbon dioxide is broken down, using energy from sunlight absorbed by the green pigment chlorophyll. Organic compounds are made and oxygen is given off as a by-product.

Pollination

The transfer of pollen grains from the stamen (male part of a flower) to the stigma (female part of a flower) of a flowering plant. This usually leads to fertilisation, the development of seeds and, eventually, a new plant.

Primary forest

Forest that has remained undisturbed for a long time and has reached a mature condition.

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